run the servomotor by inverter ?

hi all,
do anybody try to run a servomotor by inverter ?
because some inverter say they can run the PM motor,
and my understand is PM motor is synchronize motor (is it right ?),
servomotor is synchronize motor with encoder feedback to get better control !
So from derivation above, can i run the servomotor by vfd with oversize to hadle the servo peak current ?
If it work what thing i want to take care ?

thanks !

You can if the inverter is designed for it.
Example - SEW Movidrive B.
We use them on site for both Servo and Standard VSD. You have to be careful though, since the word "Servo" also means different things to different manufacturers. The standard SEW servo drive can be discribed as a "Permenant Magnet Synchronous Drive". I have also heard this type called "Brushless DC". A recent contractor and I got into an argument because he called them "DC" motors, and I didn't want DC motors. This was only settled when he gave me the part numbers and I found out it was the same Servo that I usually used (he was not a native english speaker, and turned out to be very good at setting up these things).

So, to answer your questions,
1, Some (but not all) inverters are designed to handle both standard VFD and Servo control.
2, If you want to control this type of motor, buy the correct inverter. Whether this invertor can, or should, handle other drive types is less important.
3, If you buy the correct inverter, it need not be oversized.
4, If you don't buy the correct inverter, you cannot control your servo at all (this is due to the feedback and phase angle detection that is required to drive a servo). You may even succeed in destroying your valuable inverter and/or the servo motor.
5, See www.sew-eurodrive.com for some literature on what a servo drive is, how to set it up, and everything you might want to know about the subject.

Thanks for your answer !
Yes, i think the manufacturer like to use their own term name for the servo motor, i have come across the Eurotherm call the brushless servo, and what i understand that there is dc servo motor but armature at stator (is it right ?).
Do you come across Yaskawa G7 series ?
I think ControlTechniqe Unidrive also have this kind of function !
I have Yaskawa G7 series inverter and SGM-08 800 W servo motor in my hand, i"m thinking connect them together, but before that just want to know more about PM motor and servo motor !

Thanks !!

Drives that have to calculate a 'Motor Model' will have major difficulties with a PM (Synchronous) or 3 phase Servo motor. Vector drives without a setting for a PM motor will almost never work.

That is why some inverters state they can run servo's, and others don't. Pay attention to the manufacturer documentation and UNDERSTAND it before applying something you are unsure of.

A phone call to the drive manufacturer will often get you a quick answer, but be sure to discuss your idea with an applications person there too.

Yes, i know that i should ask Yaskawa about the question at this application, but most of the time their answer are NO.
There mostly follow the catalog describtion, and then simply yes or no.
i think most of the people here are looking for more knowledge about the field we interested instead of just follow the manual or instruction from other people so why i post this topic .
i had seen a apllication on these using a vfd drive to run a synchronize motor, and there were old machine ! They just simply set the vfds run at same frquency or with certain ratio, the motor can run at steady speed and some sort of synchronize system !
There quite simple, no plc , no signal amplifier, no encoder !
The vfd is old drive that i think is just run at V/F mode .
i just wonder how it work and try to do same thing !

However thanks a lot the reply !!

I used already a servomotor with VFD.But I removed the break connections and encoder connections.VFD maximum frequency setting changed from 50hz to 400hz.

hi srik,

you change the maximun frequency to 400hz, are you need to run at so high or that is base speed ? 400 hz to 400v(assume) then mean run at 50hz output 50v ?

I run the motor at lower speeds only that means below 500 rpm .In coming supply 415 volts,50Hz.400 hz is the max.frequency set value.Base frequency is 50Hz.But Iam not used the encoder feedback.

hi srik,

whant brand and model of inverter, servo motor you use ?
any problem you encounter ?
thanks !

Actually I did it in my previous company 4 years back.Right now I dont have any information about it.But Inverter is siemens Micromaster and drive is also belongs to siemens.I tried this motor with LG and mitsubishi Inverters but I failed to run because of its maximum frequency is low( I think it is around 250Hz).While doing trial I found that there is some noise.That is the reason I changed the maximum frequeny setting from 50 hz to 400 hz with lot of attempts to reduce the noise.At 400 hz ,I found that there is no noise(sound).

try Parker-SSD-Eurotherm

The AC890 drive will connect to both induction motors
and PM servo motors.

I was just at a meeting where all the product was demonstrated,
and it looks pretty good, as a package.


www.SSDdrives.com